Calf house ventilation

[Jimfandango]

We have recently covered our yard and I believe it has lead to a couple more cases of calf pneumonia than I would usually expect.
Both sheds in question open onto said yard. They have space boarding but are pretty spacious in general. The shed is in need of reroofing so will address open ridges etc then. My current solution is to cut a large hole (2m x 1.5m) in the end of the shed (there is already space boarding on this end) and install horizontally angled slats (sort of venetian blind style) to allow more air movement.
I have questions...
Would this make a noticable difference given I already have space boarding?
Can you buy this sort of unit ready made?
Should I just buy a fan and wire the shed accordingly?
Any other suggestions?

Cheers

 

[organicguy]

A picture would be helpful.
It sounds to me that changing the end will not make enough difference.